In order to facilitate displacement of an impact compactor, when not in use, a lifting arrangement thereof provides for the rollers to be lifted with respect to the chassis structure, as permitted by the drag link that carries the axle assembly of the non-round rollers, to a level at which the said rollers are lifted off the ground and the compactor is thus displaceable on its wheels only.
The lifting arrangement referred to comprises a piston/cylinder mechanism that is operable between the chassis structure and the drag link, usually via a lifting plate pivotally located with respect to the drag link and generally below the drag link. In the latter case, an upper end of the piston/cylinder mechanism is connected to the lifting plate to effect pivoting thereof whilst, because of mechanical constraints associated with the compactor, including the requirement for a piston/cylinder with a sufficient stroke for effecting the required raising and lowering of the rollers, the other end of the piston/cylinder mechanism is located at a level beneath the general plane of the chassis structure. In order to raise the rollers with respect to the chassis structure, the piston/cylinder mechanism is extended so that the lifting plate is pivoted upwards by it to bear on the underside of the drag link to raise it. When the piston/cylinder mechanism is in its fully retracted configuration, the rollers are supported on the ground and a clearance or spacing is provided between the drag link and the lifting plate, so that the drag link can pivot with respect to the chassis without interference by the lifting plate.
In practice, particularly when compacting soft ground, it sometimes occurs that the rollers penetrate the ground to an extent that the drag link impacts on the lifting plate. This may result in mechanical damage to the lifting arrangement, e.g. punching of the piston/cylinder mechanism through the drag link. In order to reduce the risk of such damage, the clearance referred to must be maximized. To achieve this, the compactor may have the mounting location of the piston/cylinder mechanism on the chassis structure at a low level. As such, ground clearance of the lower end of the piston/cylinder mechanism is minimized, increasing the risk of damage to it due to interference by an obstacle, e.g. a rock, on the ground. Furthermore, the piston/cylinder mechanism usually is not easily visible to an operator of the compactor and, due to operator error, the piston/cylinder mechanism may not be fully retracted during use of the compactor. As such, the clearance between the drag link and the lifting plate is reduced, increasing the risk of the type of mechanical damage referred to.
The risks of damage of the above general types also are present in other variants of impact compactors including at least one non-round roller and a lifting arrangement therefor and, clearly, are disadvantages associated with such compactors. Insofar as the general configuration of an impact compactor of this general type is well known, as are the disadvantages associated with the lifting arrangement thereof, these aspects are not described in further detail herein, although the description above may be further clarified with reference to an accompanying drawing, designated FIG. 1, and a description of the drawing below.